Radio direction finder



D88. 3, 1940. F FRANSSQN 2,223,513

RADIO DIRECTION FINDER Filed Nov. 24, 1937 JPfE'D con r904 macawINVENTOR.

/MWF1I ATT'ORNEY.

Patented Dec. 3, 1940 I it.. gUNlT-El) STATES "PATENTg OFFlCE FransFransson,

Aga-Baltic Radio Akti bola Stockholm, Sweden, assignor to.

Stockholm,

In Sweden November 26, 1936 Application November24, 1937, Serial No.176,155 a 6 Claims.

I My invention relates to oscillating radio direction finders, and 'moreparticularly to phase shifting means for use in Connection therewith.

oscillating directional radio transmitter generally includes two antennasystems, for instanceone directed and one undirected system, andarrangements for repeated shifting of the phase conditioner the field"of one of the antenna systems-in relation to the phase condition of thefield'ofithe' other antenna system. The phase shifting causes the fieldcharacteristic f the antenna systems to oscillate between two difierentpositions the direction of, the so-called beam emitted by thetransmitter being determined by the intersections between the fieldcharacteristics in one position and the field characteristics in the'cther'position. It is usual to send different si nals in ,difierentpositions cf'the resultant field cha'racteristics, so thatior instance along signal is sent in one position of the field characteristicsalternatin with ashort signal in the other position. 'In the directionof the ,beam the sound is then'heard as one uninterrupted signal ofconstant'intensity. In any directions not coinciding with the"beam,on'the other hand, a short or a long'signalof greater intensity is receivedalternating with long 'or short signal, respectively, of lesserintensity. I v, i

' The function-of an oscillating directional radio receiver is analogousto the function of an OS cillating direction'al'radio transmitter. Likethe oscillating directional radio transmitter, the oscillating'directional radio receiver contains two difierent'fantenna systems; forinstance one directedand'one undirected antenna system. Duringfrepeatedshifting of the phase condition of the-current turning of the resultantfield characteristics of the antenna systems, the signal from adirectional radio transmitter is received. The direction of the" beam'is recognized by the fact that the signal isreceived with constantintensity, independently of the phase shift-ings.

f The arrangements ior'theabove mentioned phase'shi'fting are connected"to the input terminals to "one of the antenna systems of the-transmitteror receiver, respectively, for instance the undirected'syst'emL. It'isof great importance that? such 'a pliaseshifting arrangement shouldfunction with very 'great speed at the moment of phase shifting, sothat'the current changes its phase'without'being. interrupted for anyappreciable time. 'Repeat'ed interruptions of appreciabledurat'ion ofthe antenna currentcause interruptionsin the signal even in thedirection of from the two antenna systems and I the beam, whereby thedeterminings of the di rection are made'more diff cult. In addition, thephase shifting arrangements should not result in noticeable interferingsounds occurring upon phase shifting, such as audible clicking or the lllike. 'Phase shifting arrangements of the above mentioned kind areknown, which consist of four fixed condenser plates shaped as sectors ofa I circle and one additional plate, arranged to move ina circular pathin one direction and at'a constant speed along the fixed plates, one ofthe antenna systems or the direction finding apparatus being connectedto the movable plate, and the nected in pairs of two points in thetransmitter, having voltages of opposite phase. Phase shifting occursevery time the movable plate passes the space or gap betweenadjacentfixed plates. '1 In order to obtain signals of different lengthin 20 different phase positions, the fixed plates'have surfaces ofdiiferent size. v I H In view of the fact that in the known'ph'aseshifting arrangement the movable plate moves one direction at a constantspeed, and as this 25 speed must be considerable in order to 'obtain thequickest possible phase shifting; it is necessary that the surfaces ofthe fixed plates be very large in order to obtain the desired-durationofsignals of difierent phases, which involvescer- 30 tain disadvantages.Fixed condenser plates of different sizeentails, further, an undesirablecapacitive unbalance in those circuits of the transmitter to which thephase shifting arrangement is connected. a

The present invention relates to an improvement in the known phaseshifting arrangements and consists in the movable plate being given anoscillating movement back and 'forth over two adjacent fixed plates, ormovement in one di- 40 rection at a varying speed. For movement of theplate in one direction the speed should be higher during the passageover the space between the fixed plates than during the passage overone, at least, of the fixed plates. With the oscillating movement, aswell as. with the movement in the same direction at a varying speed, thesame speed, or even a higher speed of phaseshifting. can, be obtainedthan in thephase "shifting arrangement previously known, and inadditionthe fixed plates may be made considerably smaller. Also, all thefixed-plates may be of the same size and alternating long and shortsignal signs may beobtained with movement in the same direction bycausing movable condenser 10 fixed plates beingfcon- 1 5 the movableplate to of an apparatus suitable move at a lower speed when passing,for instance, every other fixed plate than when passing the other platesor the movement of the plate may be caused to take place in steps and toremain sta tionary during intervals of difierent lengths beforedifierent fixed plates. If the plate has an oscillating movement thesame result may be obtained by causing the plate to move through arcs ofdifferent amplitude over the fixed plates.

The arrangement according to the invention may be modified in such a waythat the plate described in the above as being movable is arranged as afixed plate, whereas the other plates are arranged to be movable. Allplates may be arranged to be movable in such a way that the samerelative movement desired between the plates is obtained.

Furthermore, the invention is not limited to purely capacitive phaseshifting arrangements but ma also be applied to inductive phase shiftingarrangements, or to commutator phase shifting devices and is not limitedto any particular number of fixed or movable plates.

The invention will be described further in the following with referenceto the attached drawing that shows one embodiment of the invention.

Fig. 1 is a wiring diagram of an oscillating directional radiotransmitter including a phase shifting device according to the presentinvention;

Fig. 2 is a more or less diagrammatic View of the phase shifting deviceshown in Fig. 1;

Fig. 3 is a cross-sectional view taken on the line 33 of Fig. 2;

Fig. 4 is a diagram showing certain field characteristics;

Fig. 5 is a diagram showing certain other field characteristics;

Fig. 6 is a diagrammatic View of an example for operating the phaseshifting device; and

Fig. 7 is a diagrammatic View of a modification of the apparatus shownin Fig. 6.

In Fig. 1 reference character I indicates an oscillating circuitincluded in an oscillating directional radio transmitter, in whichcircuit the signal oscillations of high frequency occur. To theoscillating circuit I, a directed antenna system consisting of twosimilar directional antennae 2 and 3' is connected through a goniometer4 and a coil 5 inductively connected to the oscillating circuit.

The oscillating circuit I is grounded at the middle point of the coil 6and the ends of the coil are connected to an undirected antenna systemconsisting of an open antenna 1 through a phase shifting arrangement inaccordance with the present invention. The phase shifting arrangementwhich in this case is shown as a capacitance includes four fixedcondenser plates 8, 9, I0 and II, and two movable plates I2 and I3; thelatter being connected to each other and to the antenna 7. The fixedplates are all of the same size and are connected in pairs to theopposite ends of the coil 6.

The construction of the phase shifting arrangement is seen more clearlyfrom Figs. 2 and 3 which show two sections taken at right angles to eachother. The movable plates are secured to a rotatable shaft I4'of adriving device I5 which is arranged to oscillate the shaft I4 and platesI2 and I 3 through an angle 21 of The antenna 1 is connected to themovable plates through a capacitive collector, consisting of condenserplates I6 secured to the shaft I4 and of fixed plates I! connected withthe antenna. Shaft I4 serves as a conductor for connecting plates I2 andI3 to plates IS.

The two ends of the coil 6 carry voltages of opposite phase. Theoscillations of the movable plates cause the antenna tobe connectedalternately to either of these ends, whereby the desired phase shiftingof the antenna current is obtained. These phase shiftings cause theresultant field characteristic of the antenna systems to oscillatebetween two different positions, as is shown graphically in Figs. 4 and5.

In Fig. 4, I8 represents the field characteristic for the undirectedantenna system I at a certain value of the current through it. Referencecharacter I 9 represents the field characteristic for the directedantenna systems 2, 3. The last mentioned field characteristic is of socalled figure-8 form. At the phase condition of the fields indicated bythe signs and a resultant cardioidic field characteristic 2!]isobtained.

Upon phase shifting of the current through the undirected antenna systemand consequent phase shifting of the field of this system, the resultantfield characteristic changes its position. The shape of the fieldcharacteristic, however, remains unchanged provided that the current isnot changed. In Fig. 5, the curve 20 indicates the position of theresultant field characteristic after the phase shifting with unalteredcurrent. In the same figure the previous position of the fieldcharacteristic is indicated by curve 20.

The directions of the beam are determined by the intersections of theresultant field characteristics 20 and 20'. As seen from Fig. 5, thedirections indicated by the lines 0-1: and 0-11 are displaced by inrelation to each other in the case where the current in the undirectedantenna system is constant, independently of the phase shifting.

For the purpose of obtaining signals of different duration in difi'erentpositions of the resultant field characteristic, the driving arrangementI5 for the movable plates of the phase shifting arrangement may be madein such a way that the movable plates will remain in one of theirextreme positions for a longer time than in the other extreme position.As a rule, however, it is more desirable to have the movable platesoscillate without any other retarding of the movement in the two extremepositions than that caused by the inertia, etc., of the movable masses,and to make the duration of the signals in the two phase positionsunequal by displacing the central points of the fixed plates in relationto the extreme positions of the movable plates, so that the movableplates will move over surfaces of different area on the difi'erent fixedplates. In the arrangement shown in Fig. 2 the central points of thefixed plates are displaced in relation to the extreme positions of themovable plates in such a way that the arcs indicated by a have a greateramplitude than the arcs indicated by b. The relation between theduration of the signals in the two phase positions is then determined bythe relation between the are a to the are I), which relation isadjustable.

In the arrangement described above a very quick phase shifting isobtained, the speed of the movable plates being very high when theseplates pass the spaces or gaps between fixed plates. This is because themass of the movable plates is comparatively small and the drivingarrangement I5 is made in such a way that the acceleration of the platesafter the reversal of movement 'in 'the two extreme preciable lengthoftime before the other ag-na .1'

positions is comparar ti ely' rap d. V I J I: I 7

An example of a suitable driving arrangement I is'shown more or lessdiagrammatically in Fig.

- 6. Reierence"character 25 designates a rotating disc mounted on ashaft 26 which is driven by a.

] slip rings 3| and 32, respectively, and are contherewith.

motor 2'|. The speed of motor 21 may be regulated in any suitablemanner, such as by the rheostat 44 included in its circuit. Disc25'includestwo sections 23' and 290i conducting material-separated byinsulating material 30." Also mounted on shaft 26 are slip rings 3| and.32 which are electrically connected to sections 28 and29,respectively.'

"A brush 33 is arranged to bear against the outer of disc,25 and isconnected to'one tera battery 34 or other source, of electriis connectedto oppositely disposed electromagnets 35 and 36. Brushes 31 and 38bearagainst nected to electro-magnets 3'5 and 36, respectively.

I A rack 39 is slidably mounted in suitable'supports 40 and is providedwith anarmature element 4| of magnetic material which is disposed so asto be attracted by either of the electromagnets 35 or 36 when the latterare energized' The rack 39 is provided with teeth 42 which mesh with apinion 43 mounted on the shaft |4 shown, for instance, in Fig. 3.

The above described dev ce operates as follows: As vdisc 25 rotatesbrush 33 is in contact first with section 28 and then with section 23thereof. When the brush is in contact, for instance, with section 28, asshown in Fig. 6, the circuit is completed from one terminal of thebattery 34 through brush 33, section 28, slip ring 3| and brush 31 toelectromagnet 35 and back to the other terminal of the battery throughthe permanent connection of the electro-magnet The electro-magnet 35 isthereby energized and armature member 4| is attracted thereto and movesthe rack 39 to the left, as

viewed in Fig. 6 to the position shown in this figure. This causesrotation of the pinion through the are 11 shown in Fig. 2. When the disc25 has rotated suificiently so that brush 33 comes into contact withsection 29, the circuit through electro-magnet 35 is interrupted and asimilar circuit is established through section 29, slip ring 32 andbrush 38 with electro-magnet 36.

Thiscauses magnet 36 to'be energized and armature element 4| isattracted thereto and. causes the rack 39 to move to the right, asviewed in Fig. 6, thereby rotating pinion 43 and shaft 4 back throughthe are c.

The speed of motor 21 may be regulated so that the sections 23 and 29,respectively, of the disc 25 pass out of contactwith the brush 33 atapproximately the instant. that armature element 4| reaches the'electro-magnet which has just been energized. With such an adjustmentof the speed of the motor, rack 39 will oscillate with but a momentarystop at its extreme positions. If it is desired to have the rackstationary for an appreciable lengthof time in its extreme positions,the speed of the motor may be reduced by means of the rheostat 44 sothat the armature element will reach the energized electro-magnet beforethe respective sections 28 and 29 of the disc have completely passed thebrush 33, whereby the armature element will be held in its extremeposition against the energized magnet for an apshown'in Fig.7, maybesubstituted for the disc 25 in-Fig. 6. In thedisc 25', 29 are unequal,section 28 '-being the larger, whereby-brush 33 'r'e'mains 1 in contactwith the section 28' for a greater length of time than it remainsincontact with section 29'. I This in' turn causes electro-magnet 35 tobe energized for a greater length of time than el-ectro-magnet 36 andconsequentlythe armature'element 4| remains inits left-hand position, asviewed in Fig; 6, fora longer periodth'an it remains in the oppositeposition. v e

s As previously mentioned, the condenser plates included in thephase'shifting arrangement may be replaced by commutators, or bydevices-known per se for inductive transmission of voltage, and thearrangements also may be modified in various other ways withoutdeviating from the principle of the invention. In the embodimentshown,the condenser plates H), H and |3may be omitted, in which casethephase shifting arrangement will consist of a movable condenser plateconnected to the antenna 1 and of two fixed condenser plates connectedto points of the circuit which carry voltages of opposite phase. Theantenna need not be connected directly to the phase shiftingarrangement, but may be connected to this through coupling elements ofany suitable kind.

The scope of my invention is not to be limited by the above description,given by way of example only, but is to be determined by the appendedclaims viewed in the light of the prior art.

What is claimed:

1. In an oscillating radio direction finder, an oscillating circuit, adirected antenna coupled to said circuit, an undirected antenna coupledto said circuit, and means for shifting the phase of the voltage appliedto one of said antennae with respect to the phase of the voltage appliedto the other antenna, including impedance elements connected to pointsof opposite phase in said circuit, animpedance element connected to saidthe sections 28' and one of said antennae, and means for moving the lastmentioned element with respect to the first connected to points ofopposite phase in said circuit, said elements being spaced with a gap'therebetween, an impedance element connected to said one of saidantennae, and means for moving the last mentioned element with respectto the first mentioned elements at a speed varying so that said lastmentioned element passes said gap at a higher speed than the averagespeed at which it passes the first mentioned elements.

3. In an oscillating radio direction finder, an oscillating circuit, adirected antenna coupled to said, circuit, an undirected antenna coupledto said circuit, and means for shifting the phase of the voltage appliedto one of said antennae with respect to the phase of the voltage appliedto the other antenna, including impedance elements connected to pointsof opposite phase in said circuit, an impedance element connected tosaid one of said antennae, and means for moving the last mentionedelement back and forth opposite to the first mentioned elements.

4. In an oscillating radio direction finder, an oscillating circuit, adirected antenna coupled to said circuit, an undirected antenna coupledto said circuit, and means for shifting the phase of the voltage appliedto one of said antennae with respect to the phase of the voltage appliedto the other antenna, including impedance elements connected to pointsof opposite phase in said circuit, an impedance element connected tosaid one of said antennae, and means for moving the last mentionedelement back and forth opposite the first mentioned elements through apath of movement the extent of which is greater opposite one of saidfirst mentioned elements than opposite the other of said first mentionedelements.

5. In an oscillating radio direction finder, an

oscillating circuit, a directed antenna coupled to said circuit, anundirected antenna coupled to said circuit, and means for shifting thephase of the voltage applied to one of said antennae with respect to thephase of the voltage applied to the other antenna, including impedanceelements connected to points of opposite phase in said circuit, animpedance element connected to said one of said antennae, and means. formoving the last mentioned element relative to the first mentionedelement and for stopping said last mentioned element for periods ofdifferent duration opposite dififerent of said first mentioned elements.

6. Device as set forth in claim 1 including a fixed capacity condenserbetween said one of said antennae and the movable element, saidcondenser including a stationary plate connected to said one of saidantennae and a movable plate connected to and movable with said movableelement.

FRANS FRANSSON.

